Electrical amplifying instrument



Dec. 27, 1949 J. J. ROOT 2,492,537

ELECTRICAL AMPLIFYING INSTRUMENT Filed Aug. 2, 1945 Aim 22x 5) Patented Dec. 27, 1949 UNITED STATES PATENT OFFICE ELECTRIGAL AMPLIFYING INSTRUMENT JDhn ,J-jRoot, New York,,.N. Application. -August 2, 1945, SerialiNo. 6086325 ,4 Claims.- (01. 171-95) This i v nt n e es o ele t ical :measincur, trumen s a m r art a l to an apparatns to -am li yine ct en r p we ntentis m y be. usedin .connectionwith meters or similar instruments which-tare designed to respond "aecording tostimulus whe her the tim u e a valtaee o a current as produced by a lphange pressure, humidity, etc., a change in motion such as is treated in manyremote indusfey-systems, or changes @Of a similar nature. The stimulus aecorded to instruments of this type saiten ex em l s i h s hat the esponse of the .instrumentis consequently limited. When conditions are to he analyzed which 'cause .a very slight change in .a recording instrument, considerable difliculties vare often -.enco untere d vb cause the indications of the change may he so small as to hinder proper interpretation. The scopeandaccuracy of these instruments are obviously affected by limitations of this nature.

Bearing the foregoing in mind, it -is an Object ojlthe present invention to provide an apparatus which shall be capable of producing a large rfi-Sponse to slight excitation.

Another object of this invention is to provide an filectromagnetically operated instrument whiehshall increase the accuracy of an indicating or translating system, Allied with this object is the provision of such an apparatus for amplitying the power applied thereto. v

Qther objects of my invention will be apparent from .the following description, it bein under, stood that the above general statements of the objects of my invention are intended t0.describe andnot to limit it in any manner.

..Referring to the drawings:

Fig, 1 is a sectional view through the device.

.Fig. 2 is an end view thereof.

Rig. .3 is a cross-section taken along the line SI he device comprises the housing In in which the nomponent parts are maintained. ,A shaft H journalled in opposite walls of housing 10 by anti-friction bearings 12 and 20. Driving power for shaft l I .is supplied byelectrie motor -l,4

through coupling [5. A pinion gear .lfiis secured to the shaft ll.

Gear 4.6is arranged toadrive gear ;I 'l enthelelectromagnetic field structure rotatably mounted in the housing II by anti-friction bearings :18 and 13, .The selectrlomagnetic field structure .com-

.pliseswa core L3 havingthe .field windings ZLa-nd ilarrangedtherein. Reels 23 of gplastic naterial reprov de the .field wi dings 'Land ti -bein wound the e A ring member .24 of magnetic material is mounted adjacent one nd of the core A3, a similar ring 25 being mounted adjacent-1t the other end.

As illustrated in Fig. 3, ring 24 fermed'wtth a series of radially disposed slots 26 whichimaa' be produced by a milling operation. Ring 25 is similarly formed, ;En d member 21 which may be formed of .hrass or the :like, :is similarly mounted within the field structure,'ithelend mem ber ll :serving as a bearing holder tor antiefriction bearing 28 and providing a trunnion {229 which is journalled in the bearing 18. Endvzmemeber 30 duplicates the construction oflmember 23, its trunnion 3| being journalled in the .rloearing 19..

A sleeve 32 serves to maintain the assemblyof the field structure. The sleeve 32 is of electrical insulating material such as Bakelite .or similar materials. Maintained around .sleevei32 isazplu rality of slip'rings 33, 34, 3 5:and :36 which may :he irictionally or otherwise secured to sleeve 3.2. Thesliprings function as pairs arranged to'enerlgize field windings .2! .and :22respectivelythrough leads. such as 1 34a and 36a.

Brushes .31., 38, 239 and ill) are provided for transmitting the electric current .to the slip rings during their rotation, the usual springs 4-! and insulating holders 42 being employed. 1

An armature :43 is provided with a shaft 44 which is '-journal1ed at one end thereof in :the hearing 2B of endmember 2i and at the other end thereof in a similar anti-friction bearing 45 in the end member 30. Armature 43 is formed at one end with a plurality of radially disposed slots 46 milled therein and :equal in number to the slots 26 of ring 24. The other end of armature 43 is likewise formed with a plurality of radial slots 41. It will be observed in Fig. '1,

however, that the slots 4! are staggered in lateral relation to the slots 46. This expedient is adopted in order to lend uniformity of electromagnetic co-action between the armature 43 and'the fieldstructure as will be hereinafter explain-ed.

Shaft 44 may be provided with an indicating ,member 48 adapted for rotation therewith; A

spiral spring 49 has one terminal thereof mounted in the housing ll) while the other terminalis Meter =1 4 is en reizedso-asvto rotate shaft My thereby causing the rotation of the electromagnetic field structure.

Electrical current generated by a meter or instrument as described above is introduced through slip rings 33 and 34 so as to energize field winding 2|, and through slip rings 35 and 36 so as to energize field winding 22 in parallel with winding 2!. The flux thereupon generated by winding 2| will fiow across the short circular air gap 50 (Fig. 3), through the ring 24, through the core l3 and thence back to the winding 2|. Since the air gap 50 may be approximately .005" wide or even less, a magnetic path of high permeability is provided.

The electromagnetic co-action between the ring 24 and armature 43 will be such that the slots 46 of the armature will attempt to align them-. selves with the slots 26 of the ring since in that position the permeability of the magnetic path is greatest. This action, in effect, locks the armature to the rotating field structure so as to partake of its motion. It is apparent that the lock-' ing effect is a function of the flux density which is in turn dependent upon the current flowing through the winding. Thus, motion proportional to the current flow is imparted to the armature 43.

The parallel current flowing in the winding 22 produces flux which takes a similar path as the other end of the device. However, since the slots in the ring 25 are aligned with the slots 26 of ring 24 while the respective slots at each end of armature 43 are misaligned, the armature 43 will be locked in an intermediate position wherein the adjacent slots of the armature and rings are overlapping. While the locking effect is independent of the staggered nature of armature slots 41, this disposition of the slots provides a smoother, more uniform action and avoids jerk' ing of the armature when the windings are energized. However, it is unnecessary to so misalign the slots unless lack of uniformity of electro-magnetic co-action must be avoided.

The motor I4 is arranged to rotate in such a.

direction that the electro-magnetic coupling of the field structure and armature 43 will cause the armature to wind up the spiral spring 49. The

spring 49 is arranged to balance this torque so ment will depend largely upon the nature of spring 49. If it is a stiff spring, large currents will be required to actuate the indicator whereas if it is a delicate spring, minute currents may by measured. Similarly, the spring may have many turns so as to permit the indicator to effect many revolutions before a small current is balanced. Thus, a high degree of amplification can be achieved in that the indicator 48 may be capable of as high as ten or more revolutions in response to slight excitation applied to the field structure.

The advantages of such an instrument will be apparent to those skilled in the art. For example,

a small current can, through many ampereturns, generate an electromagnetic flux of high magnetomotive force. It will be observed that the force applied to the armature is not decreased during the rotation of the indicator 48. In many instruments wherein magnetomotive force acts upon a movable member, the resulting movement creates a gap of increasing reluctance so that the force necessarily diminishes as the movement progresses. In the instant invention, however, the reluctance of the air gap 50 is constant and relatively slight. If desired, a reduction gearing arrangement may be employed in conjunction with indicator 48 so that a coarse scale as well as a fine scale may be provided, a second pointer indicating larger units than that indicated by pointer 49. Similarly, if reciprocating rather than rotating motion of the pointer is desired, the shaft 44 may actuate a rack.

I have shown a preferred embodiment of my invention but it is obvious that numerous changes and omissions may be made without departing from its spirit. For example, while I have illustrated the use of two field windings, it is apparent that a single winding will be efiective or that the windings shown may be series instead of parallel connected. With such construction the staggered nature of the armature slots could be dispensed with.

It is further possible to reverse the described transmission of motion in that a motor may be arranged to drive the armature. This would serve to apply a load to motor [4 when excitation was applied to the field structure and the device would function as a dynamometer as will be apparent to those skilled in the art I claim:

1. An article of the character described comprising an electromagnetic field member having a series of radially disposed slots formed at both ends thereof, driving means for rotating said field member, an armature member mounted concentrically of said field member and arranged for rotation relative thereto, said armature having a series of radially disposed slots at both ends thereof so as to be respectively concentric and adjacent to said series of field member slots" whereby an air gap separates the respective slots of said field member and armature, means to introduce electrical excitation to said field member so as to generate magnetomotive force proportional to said electrical excitation, said magnetomotive force being operative across said air gaps to urge said respective slots of said field member and armature into alignment so as to 3. A device according to claim 1 wherein the respective series of slots at the ends of said arma ture are relatively staggered.

4. An article of the character described comprising an electromagnetic field member having slots formed therein, an armature member mounted for rotation relative to said field mem-"' ber, said armature member having slotsformed" therein concentrically arranged in respect to and adjacent to said field member slots, driving means for rotating one of said members, means to energize said field member by an electric current so as to generate an electromagnetic field having a magnetomotive force proportional to said electric current, said magnetomotive force urging said respective slots into alignment whereby said armature member is electromagnetically locked to said field member by a force proportional to said electric current so as to impart rotation of said driven member to the other member to an extent depending upon the value of said electric current, an indicator on said other member, and a spiral spring having one terminal fixed and the other connected to said other member so as to be Wound due to the imparted rotation thereof whereby said spiral spring tends to oppose said imparted rotation and the winding of said spring depends upon the relative value of said opposing forces.

JOHN J. ROOT.

REFERENCES CITED The following references are of record in the file of this \patent:

UNITED STATES PATENTS Number Name Date 454,832 Bennett et al June 23, 1891 993,910 Thomson May 30, 1911 1,382,694 Towar June 28, 1921 1,721,853 Boykow July 23, 1929 1,911,960 Lipman May 20, 1933 2,217,088 Wilson et a1. Oct. 8, 1940 2,248,495 Dupy July 8, 1941 

